I'm ripping to aiff using XLD
all file tags are entered in XLD before ripping
cover art too is added in XLD before ripping

then I use Tag to check if all is fine (eventually I correct typos) and to Calculate Replay Gain

but sometimes, the instant I hit save in Tag... one or two track's cover art does not show anymore (was showing just fine after ripping) in finder's preview
again: I do not touch cover art in Tag, I only use it to add Replay Gain values

hope you have figured out, in the files I sent you, what's up. did you?